This invention relates to storage systems for pressurized gasses, and, in particular, to an expandable, collapsible ambulatory storage system.
High-pressure gases are typically stored in steel or aluminum containers. For example, oxygen is stored in steel or aluminum containers (or cylinders) for use in aviation (spacecrafts, private, military and commercial airplanes), by scuba divers, in hospitals, emergency vehicles, and by patients requiring oxygen therapy. In aviation, oxygen is supplied in specially designed high-pressure canisters.
In the medical field supplemental oxygen is prescribed to patients who suffer from a variety of respiratory disorders, due to respiratory insufficiency or respiratory failures such as, obstructive pulmonary disease, chronic bronchitis, interstitial or restrictive lung disease, emphysema, congestive heart failure and during surgical operations. The typical modes of oxygen delivery are concentrators that concentrate atmospheric oxygen, pressurized canisters, high pressure cylinders made of steel or aluminum, or liquid oxygen systems that convert liquid oxygen to a gaseous state for ambulatory or domicile use. High-pressure cylinders are often wrapped with other high-tensile strength material for structural reinforcement such as carbon fiber, or other materials.
The steel or aluminum cylinders store gases at a range of pressure that depends on application. Supplemental oxygen storage devices for example store oxygen at a pressure of up to 3000 psi (pounds per square inch). For therapeutic use or other applications the pressure is lowered using a pressure regulator. In the case of therapeutic application it is regulated down to atmospheric pressure.
Existing gas storage devices suffer from many limitations, including economic, safety, ergonomic, human factors and environmental drawbacks. Aluminum or steel cylinders are expensive to manufacture and are not environmentally compatible. They are costly to distribute because of their weights and pose a safety hazard if ruptured or dropped. The economic attractiveness of these devices is diminished in a flat reimbursement healthcare system (such as under HMO's) and in situations where it is difficult to supply patients with the required cylinders, such as patients in remote locations.
Furthermore there is a high acquisition or capitalization cost associated with purchase of infrastructure needed for entry into this business because of the per-unit cost of steel or aluminum. This poses barriers to entry and ultimately limits competition with a resulting penalty in cost of care. These issues are compounded by the high cost of manufacture.
From a safety point of view, high-pressure storage devices made of steel or aluminum can fragment when ruptured. The fragments are effectively shrapnel, and can cause severe injury or even death to people in the vicinity of the cylinder when it ruptures.
Notwithstanding the long-term rehabilitative benefits of oxygen, patient compliance as well as adoption of high-pressure containers as a supplemental oxygen source has been a problem. The existing cylinders are not portable (they are too heavy), are uncomfortable to carry, or are esthetically displeasing. In response, several lightweight high-pressure gas storage containers made from a synthetic material have been proposed.
Scholley (U.S. Pat. No. 4,932,403) describes a container in the form of a continuous length of hose incorporating a series of expanded diameter storage sections and flexible connecting sections into its length. The storage chambers are interconnected by narrow bent conduits and attached to the back of a vest that can be worn by a person. The device embodies a pressure regulator at one end, which regulates supply of compressed gas to the mouth of the user.
Scholley's container includes an interior liner, constructed of flexible material, covered by braided fibers, which may be formed of a synthetic material such as nylon, polyethylene, polyurethane, tetrafluoroethylene, or polyester. The liner is covered with a reinforcing material, such Kevlar (an aramid fiber having a tensile strength three times the strength of steel) and impregnated by a protective coating of material such as polyurethane.
The Scholley container suffers from several limitations, making it impractical for high-pressure applications. The tubular shape of the independent containers does not provide adequate reinforcement for storage of high-pressure gas, and the narrow, bent conduits are unreliable when used in cyclical and repetitive filling and emptying applications. Furthermore it is costly and difficult to manufacture because of the required fittings, geometry of the conduits, amount of material and pieces that must be assembled. Another limitation of the Scholley container is that when the tubular high-pressure gas device is installed longitudinally within a vest, it is impractical. When the storage device is pressurized, it is as hard, rigid, and difficult to bend; and thus cannot be worn as clothing that overlaps the body.
Cowley (U.S. Pat. Nos. 3,491,752 and 3,432,060) describes a lightweight flexible pressure container made in the form of a coiled spiral tube. While compact, the device is limited to applications of short duration. Storage capacity cannot be increased by using a larger tube due to flexibility and weight penalties.
Farr (U.S. Pat. No. 1,288,857) describes a life preserver made from multiple interconnected cylinders, that are made from rubber, cloth or fabric. The geometry and configuration of the connecting pipes and cylinders pose severe challenges to manufacture and personal use, and as a result is infeasible.
Alderfer (U.S. Pat. No. 2,380,372) describes a portable container system that is built into a parachute pack to provide oxygen to parachutists. The container system includes a length of hose in the form of concentric coils that conform to the shape of the seat.
Warnke (U.S. Pat. No. 3,338,238) describes a multi-cell container which is flat or oval-shaped in cross-section. This container suffers from similar limitations as the other containers; i.e., the inability and/or expense to manufacture, and inability to conform to the body for personal use.
Sanders (U.S. Pat. No. 6,116,464) describes a container system, consisting of interconnected ellipsoidal chambers. A tubular core consisting of gas exchange apertures (for evacuation) connects the chambers. The Sanders container is also very expensive to manufacture.
Arnoth (U.S. Pat. No. 4,964,405) discloses a vest which can be worn by emergency personnel. The vest has a self-contained unit with a source of oxygen. Oxygen is stored in pressurized canisters in the front of the vest. The back of the vest includes collapsible channels through which the oxygen passes, and which contain CO2 scrubbers to remove CO2 from the gas being inhaled by the emergency personnel. These channels do not form or define pressurized containers for the oxygen.
No one, to my knowledge, has developed a light-weight pressurized container which is economical to manufacture, and is easily carried by the user.